CN108424352B - Refining method of biodiesel byproduct glycerol - Google Patents

Refining method of biodiesel byproduct glycerol Download PDF

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CN108424352B
CN108424352B CN201710077801.1A CN201710077801A CN108424352B CN 108424352 B CN108424352 B CN 108424352B CN 201710077801 A CN201710077801 A CN 201710077801A CN 108424352 B CN108424352 B CN 108424352B
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glycerol
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biodiesel
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entrainer
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CN108424352A (en
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帅放文
王向峰
章家伟
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Hunan Er Kang Pharmaceutical Co Ltd
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    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
    • C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C29/00—Preparation of compounds having hydroxy or O-metal groups bound to a carbon atom not belonging to a six-membered aromatic ring
    • C07C29/74—Separation; Purification; Use of additives, e.g. for stabilisation
    • C07C29/76—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment
    • C07C29/86—Separation; Purification; Use of additives, e.g. for stabilisation by physical treatment by liquid-liquid treatment
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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    • Y02P20/00—Technologies relating to chemical industry
    • Y02P20/50—Improvements relating to the production of bulk chemicals
    • Y02P20/54—Improvements relating to the production of bulk chemicals using solvents, e.g. supercritical solvents or ionic liquids

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Abstract

The invention discloses a refining method of biodiesel byproduct glycerol, which comprises the following steps: adding the waste liquid of the biodiesel into an extraction tank of a supercritical extraction instrument, determining the temperature, the pressure, the flow, the entrainer and the extraction time, extracting, obtaining a crude product from the supercritical fluid extraction instrument, and introducing the crude product into a continuous evaporation tank to obtain the final refined glycerol. The method has the advantages of simple process, high glycerol extraction efficiency, high product purity and high utilization rate of the biodiesel waste liquid, and improves the utilization value of the glycerol, thereby reducing the production cost of the biodiesel.

Description

Refining method of biodiesel byproduct glycerol
Technical Field
The invention belongs to the field of glycerol preparation, and particularly relates to a refining method of byproduct glycerol in biodiesel preparation.
Technical Field
Along with the change of the world energy structure, people are actively developing, popularizing and applying green energy with small side effect and less pollution in order to solve the problems of shortage of petroleum resources, environmental pollution and greenhouse effect 3, strategic reserve of resources and surplus of grain and oil. Biodiesel is a high-quality substitute for petroleum diesel, and has received wide attention from the world due to its environmental friendliness and renewability. Along with the continuous heating of the investment heat of the biodiesel at home and abroad in recent years, the yield of the biodiesel is greatly improved, and simultaneously, a large amount of crude glycerol is also by-produced. As the main by-product glycerol in the biodiesel production process, about one ton of crude glycerol is by-produced for every ten tons of biodiesel produced. At present, the industrial production mainly adopts an alkali catalysis ester exchange method, the upper layer is a methyl ester layer, and the biodiesel is obtained after refining; the lower layer is a byproduct rich in glycerol. One of the main problems faced in the development of biodiesel at the present stage is the reduction of the production of finished products, and one of the ways is to fully utilize the glycerol which is a byproduct in the biodiesel production process.
Glycerol, commonly known as glycerol, is an important light chemical raw material and is widely applied to various industries. As humectants and solvents as in the tobacco industry; the method is used for producing essence and toothpaste in daily chemical industry; as solvents and lubricants in the pharmaceutical industry; in the food industry for the manufacture of monoglycerides, humectants and sweeteners; in the paint industry for the production of phenolic resins and alkyd resins, etc. With the continuous development of national economy in China, the market demand of glycerol as an important chemical product of the national civilization is continuously increased, and particularly, the demand in the paint, cosmetic and pharmaceutical industries is increased year by year.
The crude glycerol is a product in the production of biodiesel, however, the byproduct crude glycerol obtained by producing the biodiesel in the prior art has dark color, more impurities, difficult refining and low quality of finished products. The main impurities are waste catalyst, various salts generated after neutralization reaction, residual methanol, methyl ester, grease \ fat, soap and free fatty acid. Therefore, the delicate purification of the crude glycerol is a key link for effectively utilizing the byproduct glycerol of the biodiesel. At present, the methods for refining crude glycerol mainly comprise an ion exchange method, a reduced pressure distillation method and a membrane separation method.
The ion exchange method has important application in the production of the glycerol, most of food-grade and medical-grade glycerol is finally obtained by refining the ion exchange resin, however, the glycerol is refined by directly adopting the ion exchange resin, the resin is quickly saturated and inactivated, and the regeneration of the resin can generate a large amount of acid-base wastewater to pollute the environment.
Distilling under reduced pressure, wherein the boiling point of the glycerol is as high as 290 ℃ under normal pressure. The glycerol is refined at relatively low temperature by adopting a reduced pressure distillation method in laboratories and industry to obtain the high-purity glycerol. The purification of glycerol by distillation under reduced pressure is well established, however, the method still has some disadvantages. In practical application, glycerin often has side reactions to affect the purity, color and yield of glycerin, and high temperature causes large energy consumption in the refining process. Therefore, strict control of the temperature is important in the actual operation process of the reduced pressure distillation method, and the distillation temperature and the distillation pressure are automatically controlled in a proper range in the future or by developing an intelligent control system so as to improve the refining efficiency and reduce the energy consumption.
The membrane separation technology becomes a new technology for refining the glycerol, and the technology is green and environment-friendly and can bring certain economic benefits. However, in the membrane separation, a filter medium with certain selective permeability is used for separating and purifying substances, and due to the characteristic difference of the substances in the separation process, certain influence is caused on the membrane separation operation, particularly concentration polarization, membrane pollution and the like, so that the separation efficiency is greatly reduced. This still requires research for relevant applications.
As mentioned above, the reduced pressure distillation method has large energy consumption for refining glycerol, and the purity of the glycerol is greatly influenced by the temperature; compared with the method for refining the glycerol by the reduced pressure distillation method, the ion exchange method can save energy and reduce the loss of the glycerol, and can avoid the side reaction of the decomposition or polymerization of the glycerol at high temperature, so that the prepared glycerol has higher quality. However, the purity of the refined glycerol by the ion exchange method is also influenced by the pretreatment process, and meanwhile, a large amount of environmental pollutants such as waste acid, waste alkali and the like are generated in the regeneration process of the ion exchange resin; compared with the two methods, the membrane separation technology has incomparable advantages and wide application prospect, but most of the glycerol refining methods are not industrially mature and applied, the stability and the economy of the glycerol refining methods are still to be investigated and improved, and the research on related applications of the glycerol refining methods is still needed.
Disclosure of Invention
The invention provides a method for refining biodiesel byproduct glycerol, aiming at solving the technical problems in the refining and purifying process of biodiesel byproduct glycerol at present.
1. A refining method of biodiesel by-product glycerol comprises the following steps:
a: adding the biodiesel waste liquid into an extraction tank of a supercritical extraction instrument, and determining the temperature, the pressure, the flow, the entrainer and the extraction time for extraction;
b: and (3) obtaining an extraction product from the separation tank, introducing the extraction product into a continuous evaporation tank at a uniform speed, and finally obtaining the refined glycerol at a certain temperature and vacuum degree.
Further, the supercritical fluid used is CO2、NO2Or supercritical fluid of the freon series, preferably CO2。
Further, in the step A, the temperature is 25-55 ℃, the pressure is 5-40 Mpa, the flow is 0.5-50L/h, and the extraction time is 2-10 h.
Further, the entrainer in step a may be one or more of methanol, ethanol, acetone, ethyl acetate, chloroform, and n-butanol.
Further, in the step B, the vacuum degree of the evaporator is 0.5-100pa, the distillation temperature is 20-80 ℃, and the time is 30-60 min.
The supercritical fluid has good permeability and solubility, can quickly extract effective components from materials, can selectively separate out high-purity solute by selecting proper extraction solvent and working conditions, thereby improving the quality of products, and is difficult to extract when more polar groups are used for compounds with polar groups (-OH, -COOH and the like), so that polyhydric alcohols, polybasic acids and polyhydroxy aromatic substances are difficult to dissolve in the supercritical fluid. A third component is added to the binary system of active ingredient and supercritical fluid to change the solubility of the original ingredients, and the third component with the changed solubility of solute is often referred to as an entrainer in the study of supercritical fluid extraction. The entrainer in the invention can be one or more of methanol, ethanol, acetone, ethyl acetate, chloroform and n-butanol, and improves the solubility of glycerol. However, as entrainer is used, some extracts may have entrainer residues, so that the glycerol extracted by the supercritical fluid is introduced into a continuous evaporation tank at a uniform speed, and the refined glycerol is finally obtained at a certain temperature and vacuum degree.
Advantageous effects
1、CO2The gas is an inactive gas, does not generate chemical reaction in the extraction process, belongs to a non-combustible gas, and is tasteless, odorless, nontoxic and very good in safety; CO 22The gas has low price, high purity and easy preparation, and can be repeatedly recycled in production, thereby effectively reducing the cost.
2. The supercritical fluid extraction is the cleanest extraction method, so that the existence of harmful substances to human bodies and the pollution to the environment in the extraction process are prevented, the process is simple and easy to master, and the extraction speed is high.
3. According to the invention, the biodiesel byproduct glycerol is refined, the yield is high, the purity is high, and the utilization rate of the glycerol is improved, so that the production cost is reduced.
Detailed Description
The following examples are intended to illustrate the invention without further limiting it.
Example 1
Pouring the waste liquid of biodiesel prepared by alkali-catalyzed transesterification into an extraction tank of a supercritical extraction apparatus, and adding CO2Entrainer methanol with volume ratio of 100:1, set temperature of 35 ℃, pressure of 10Mpa, flow rate of 5L/h and extraction time of 6h, supercritical fluid crude glycerol obtained from the separator is added into a continuous evaporator at constant speed, vacuum degree is 50pa, distillation temperature is 70 ℃, condensation temperature is 10 ℃, refined glycerol is obtained, recovery rate of glycerol is 98.5%, and purity is 99.7%.
Example 2
Pouring the waste liquid of biodiesel prepared by alkali-catalyzed transesterification into an extraction tank of a supercritical extraction apparatus, and adding CO2Entrainer ethanol-methanol with volume ratio of 100:1, set at 40 deg.C, pressure of 12Mpa, flow rate of 5L/h, extraction time of 6h, adding supercritical fluid crude glycerol obtained from the separator into a continuous evaporator at uniform speed, vacuum degree of 40 pa, distillation temperature of 75 deg.C, condensation temperature of 10 deg.C to obtain refined glycerol, wherein the recovery rate of glycerol is 98.8%, and the purity is 99.9%.
Example 3
Pouring the waste liquid of biodiesel prepared by alkali-catalyzed transesterification into an extraction tank of a supercritical extraction apparatus, and adding CO2Entrainer methanol-n-butanol with volume ratio of 100:1, set temperature at 35 deg.C, pressure at 12Mpa, flow rate at 5L/h, extraction time at 6h, adding supercritical fluid crude glycerol obtained from separator into continuous evaporator at uniform speed, vacuum degree at 80 pa, distillation temperature at 70 deg.C, condensation temperature at 10 deg.C to obtain refined glycerol, wherein the recovery rate of glycerol is 98.2%, and the purity is 99.8%.
Example 4
Pouring the waste liquid of biodiesel prepared by alkali-catalyzed transesterification into an extraction tank of a supercritical extraction apparatus, and adding CO2Entrainer methanol-acetone with volume ratio of 100:1, setting temperature at 35 deg.C, pressure at 10Mpa, flow rate at 5L/h, extraction time at 6h, separating in separatorThe crude glycerol of the supercritical fluid is added into a continuous evaporator at a constant speed, the vacuum degree is 50pa, the distillation temperature is 70 ℃, the condensation temperature is 10 ℃, refined glycerol is obtained, the recovery rate of the glycerol is 98.8 percent, and the purity is 99.9 percent.
Comparative example 1
Clarifying 100L of waste liquid of biodiesel, adding 50L of phosphoric acid with the concentration of 3mol/L as a cationic clarifying agent to obtain refined waste liquid, concentrating, adding 10L of phosphoric acid with the concentration of 3mol/L as a cationic clarifying agent to perform secondary clarification, adding activated carbon with the mass ratio of 1:0.5 to the solution to perform decoloration, and finally distilling a glycerol product under reduced pressure, wherein the recovery rate of the glycerol is 70 percent, and the purity is 95 percent.
Comparative example 2
Pouring the waste liquid of biodiesel prepared by an alkali-catalyzed transesterification method into an extraction tank of a supercritical extraction apparatus, adding no entrainer, setting the temperature at 35 ℃, the pressure at 12Mpa, the flow at 5L/h and the extraction time at 6h, adding the supercritical fluid crude glycerol obtained in a separator into a continuous evaporator at a constant speed, wherein the vacuum degree is 80 pa, the distillation temperature is 70 ℃, the condensation temperature is 10 ℃, and the refined glycerol is obtained, wherein the recovery rate of the glycerol is 78.2%, and the purity is 96.8%.
Comparative example 3
Reference (A) toPreparation of biodiesel and by-product crude glycerin thereof Study of separation and refining Process [ J]Biochemical engineering, 2006, 40(1):1-4.): weighing 100g of crude glycerol, transferring the crude glycerol into a beaker, adding 20-30 g of diluent, fully stirring, neutralizing with phosphoric acid until the pH value of the solution reaches 4-7, centrifugally separating the neutralized solution, dividing the separated solution into 3 layers, collecting the middle layer liquid, and transferring the middle layer liquid into a three-neck flask with a vacuum distillation device, a thermometer and a reflux condenser. And distilling at 70 ℃ under normal pressure to recover methanol, and distilling at 164-204 ℃ under reduced pressure to obtain a fraction, namely refined glycerol. Under the condition, the yield of the glycerol can reach 31.2 percent, and the purity reaches 97.52 percent. (ref.)
As can be seen from examples 1-4 and comparative examples 1 and 3, the present invention greatly improves the recovery rate and purity of the biodiesel byproduct glycerol.
As can be seen from examples 1-4 and comparative example 2, the recovery and purity of glycerol can be improved by using an entrainer in the present invention. The method is described in the' second part of the national Pharmacopeia 2015 year edition
TABLE 1-4 detection of Glycerol refining impurity content in product of examples 1-4
Figure 304466DEST_PATH_IMAGE001
As described above, the impurities of the glycerol obtained in examples 1 to 4 were detected (see "chinese pharmacopoeia 2015 edition" for methods and standards), and the following results were obtained: the refined glycerol meets the standard of Chinese pharmacopoeia, and the yield and the purity are higher.

Claims (1)

1. A refining method of biodiesel by-product glycerol comprises the following steps:
a: adding the biodiesel waste liquid into an extraction tank of a supercritical extraction instrument, and determining the temperature, the pressure, the flow, the entrainer and the extraction time for extraction; wherein the supercritical fluid is CO2The temperature is 25-55 ℃, the pressure is 5-40 Mpa, the flow is 0.5-50L/h, the extraction time is 2-10 h, and the entrainer can be one or more of methanol, ethanol, acetone and n-butyl alcohol;
b: obtaining an extraction product from the separation tank, passing through a continuous evaporation tank at a uniform speed, and finally obtaining refined glycerol at a certain temperature and vacuum degree; wherein the vacuum degree of the evaporator is 0.5-100pa, the distillation temperature is 20-80 ℃, and the time is 30-60 min.
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CN101182281A (en) * 2007-12-18 2008-05-21 昆明理工大学 Method for refining biodiesel byproduct glycerin
CN101423456A (en) * 2008-12-02 2009-05-06 昆明理工大学 Recovery and purification method of glycerol as by-product of biodiesel production prepared by Jatrohpa curcas seed oil
CN102030614A (en) * 2010-11-15 2011-04-27 上海大学 Method for purifying by-product glycerin of biodiesel and synthesizing glycerol triacetate

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US4683347A (en) * 1986-06-23 1987-07-28 Shell Oil Company Glycerine purification process
CN101107991A (en) * 2007-08-24 2008-01-23 清华大学 Method of extracting carotenoid and edible glycerol from Dunaliella sallina
CN101182281A (en) * 2007-12-18 2008-05-21 昆明理工大学 Method for refining biodiesel byproduct glycerin
CN101423456A (en) * 2008-12-02 2009-05-06 昆明理工大学 Recovery and purification method of glycerol as by-product of biodiesel production prepared by Jatrohpa curcas seed oil
CN102030614A (en) * 2010-11-15 2011-04-27 上海大学 Method for purifying by-product glycerin of biodiesel and synthesizing glycerol triacetate

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